This invention relates to a method and apparatus for shriveling call terminations to a surveillance target's mobile and more particularly to forcing the call path for these terminations through a predetermined MSC for surveillance.
While the invention is particularly directed to the art of ANSI-41 and MAP wireless telecommunications networks, and will be thus described with specific reference thereto, it will be appreciated that the invention may have usefulness in other fields and applications.
As is known in the art, the Communications Assistance for Law Enforcement Act (CALEA) prescribes the statutory obligations of a telecommunications carrier to assist a Law Enforcement Agency (LEA) in executing electronic surveillance pursuant to a court order or other lawful authorization. Under CALEA, the telecommunications carrier is generally obliged to provide a suitable means for LEAs to monitor the calls of telephone subscribers when the LEAs are duly authorized under the law to engage in such surveillance of the subscribers. CALEA simply seeks to ensure that after an LEA obtains the appropriate legal authority, the telecommunications carrier will have appropriate capability, and sufficient capacity, to assist the LEA regardless of their specific systems or services. Accordingly, various implementations have been developed to enable telecommunications carriers accommodate CALEA.
Until recently, a called party's “home” destination network node has typically always been involved in calls made to the calling party in ANSI-41 wireless telecommunications networks in the United States. The “home” destination network node, referred to herein as the home network node, can be either a home MSC or similar switching apparatus for wireless originated calls, or a local gateway switch for wire line originated calls.
The home network node would send a Location Request Query such as a Location Request Invoke message to the HLR and then route the call to the appropriate serving MSC, regardless of its location, using a Temporary Local Directory Number received in the Location Request Return Result.
For example, a call from a Miami based origination to a mobile having a home network node (an MSC) in New York that is currently roaming in Seattle will first be routed to the mobile's home network node in New York and then delivered to the serving Seattle MSC, instead of having initially been routed directly from Miami to Seattle. Even more illuminating would be a call from that same Miami based originator to that same New York customer actually sitting next to that Miami originator. Again, the call will first be routed to New York and then back to Miami.
Consequently, today's CALEA methods, at least as they apply to mobile terminations, that is calls made to a mobile phone, are based upon this assumption that the call, whether it is a wire line originated call or a wireless originated call, will first be routed to the home network node before any attempts will be made to determine the actual serving location and treatment for that called mobile. Thus LEAs have typically arranged CALEA surveillances at the target's home network node since wherever the target may be roaming with their mobile, they can be locally shriveled at their home network node, such as New York in this example.
However, in an effort to alleviate the unnecessary utilization of network resources, some networks allow subscribers to have their call deliveries initiated from any MSC in the network, not just from the subscriber's home MSC. That is, for a given subscriber, a Location Request Invoke could be sent to the HLR from any MSC. In ANSI-41 networks, this can be referred to as being LOCREQ'ed from any MSC. For the Miami call examples above, the Location Request Invoke would be sent from Miami, not from the New York home network node, and the Location Request Return Result would cause the call to be routed directly to Seattle, or as a local mobile-to-mobile call at the Miami MSC, respectively, completely eliminating any signaling to the New York network node.
While these changes to the signaling path may improve efficiency, they pose problems for LEAs intending to survey a target's mobile. Unless the LEAs have placed surveillances for this mobile at all MSCs in the network, terminating call data and content will be unavailable to them if the target is LOCREQ'ed from an MSC that does not have a surveillance set-up for the target mobile.
Local law enforcement agencies, for example the New York Police Department, may have limited jurisdiction, and may not be able to easily place a surveillance at, for example a Miami MSC. Further, it may be significantly cheaper and easier for some LEAs to be able to choose a specific MSC for all or most surveillances of call terminations, thereby saving on deploying surveillance links and hardware at multiple MSCs.
Therefore, a method and apparatus are needed to solve the problem of providing terminating surveillance information from a single fixed MSC, while still meeting the constraints of CALEA which require that information about surveillance may not be shared over public interfaces such as ANSI-41.
The present invention contemplates a new and improved system and method for shriveling mobile terminated calls that resolves the above-referenced difficulties and others.